Jersey Geology Trail
The soils of Jersey are varied but have not been mapped in detail. They overlie glacial head and loess and most soil profiles display the standard a, b, and c intervals (horizons), from soil variably rich in humus down into subsoil and into the weathered bedrock horizon. Sometimes, this can be confused with an angular head deposit which can lie directly on bedrock.
Topographically, Jersey is a plateau sloping southwards with the surface rising from c.50m above steep cliffs in the south to c. 145m in the north from where it drops quickly down to steep cliffs c.100 m high. This plateau is deeply incised by long, mis-fit valleys with flat floors containing today's south-flowing streams. These rise just below the northern interfluve while on the other sides (north, west and east), the streams have shorter profiles and generally V-shaped sections, dropping into the sea via waterfalls.
In general, the plateau surface consists of soils varying from sandy over the granites to clay loams over the shales and the generally acid volcanics, the latter not providing the fertile soils of weathered basalts elsewhere in the world. The valleys and flat coastal marsh (wet) land areas are generally composed of silts and muds except where they have been overlain by wind-blown (aeolian) sand.
Soil investigations were made as part of an agricultural survey for the Jersey Island Plan of 1983 and were reported by Rural Planning Services (1983a; 1983b). Further detailed information was comprehensively added by Jones, Keen, Birnie and Waton (1990) in an excellent Société Jersiaise publication (see below). In brief, the investigations identified seven Series related to the bedrock and drainage systems, but it should be remembered that in terms of organic content, they have been beneficiated by vraic over many years. The seven Series are summarised as follows;
1. The Trinity Series consists of silty and fine sandy loams on loess, loessic head and some fine blown sand.
2. The Colombier Series consists of silt to fine sandy loams developed on the Jersey Shale Formation and on its Pleistocene deposits derived by weathering.
3. The Noirmont Series consists of sandy loam developed over granite.
4. The Samarès Series comprises silty to fine sandy loams developed on loess or blown sand.
5. The Rozel Series consists of silty to sandy loams developed over head or igneous rock.
6. The Radier Series consists of silty clay-loams to fine sandy loams which have developed over alluvium or other drift in the valleys.
7. The St. Ouën Series varies from loamy sands to sandy loams over blown sand with little organic matter.
Maps showing the Soil Series distribution are only presented for seven areas along the south coast from the Airport area to St. Clement (Rural Planning Services, 1983b, Geographical Survey). These are described and summarised (loc. cit. pp. 4 - 9). These reports and the one following were kindly made available by the Environment Division (PE) of the States of Jersey.
In contrast, the comprehensive results of a geochemical reconnaissance survey (Walker, 1999) give a detailed picture of the concentration of nineteen elements in the Jersey soil profile from samples on a one per sq. km grid within depth intervals of 0 - 15cm, 15 - 30cm and 30 - 45cm. The types of soil within these intervals were not identified and the conclusions were that it was difficult to distinguish whether the presence and distribution of the elements was a result parent rock influence or anthropogenic activities (loc. cit. p. 77). In general, soils overlying the andesite and rhyolite rocks have higher concentrations of a range of elements than those over the granites and shales, and higher concentrations of Mg, Al, Cr, Ni, K, Zn and P were found in soils overlying the volcanic rocks.
Rural Planning Services, 1983a, b. Jersey Island Plan Agricultural Survey: a. Technical Report; b. Geographical Survey. Didcot: Rural Planning Services.
Jones, R., Keen, D., Birnie, J., & Waton, P. 1990. Past Landscapes of Jersey; Environmental Changes During The Last Ten Thousand Years. Société Jersiaise.
Walker, V. 1999. A Geochemical Reconnaissance Survey of Soils in Jersey (C.I.). Unpublished MSc. thesis, Imperial College of Science Technology and Medicine, University of London.